Change Channel to Source (#12)

* Ensure channel detail lookup doesn't download the video - oops

* Ran the needful migrations for replacing channels with sources

* got media source test back working

* channel tasks test

* Media indexing worker test

* media tests

* Got all tests working except controller tests

* got all tests working

* Renamed Channel struct to Source

* renamed ChannelTasks

* More renaming; renamed channel details module

* Removed Channel yt-dlp module, instead throwing things in the VideoCollection module

* Renamed what looks like the last of the outstanding data

.iex.exs

@@ -3,7 +3,7 @@ alias Pinchflat.Repo
 alias Pinchflat.Tasks.Task
 alias Pinchflat.Media.MediaItem
 alias Pinchflat.Media.MediaMetadata
-alias Pinchflat.MediaSource.Channel
+alias Pinchflat.MediaSource.Source
 alias Pinchflat.Profiles.MediaProfile
 
 alias Pinchflat.Tasks
@@ -11,4 +11,4 @@ alias Pinchflat.Media
 alias Pinchflat.Profiles
 alias Pinchflat.MediaSource
 
-alias Pinchflat.MediaClient.{ChannelDetails, VideoDownloader}
+alias Pinchflat.MediaClient.{SourceDetails, VideoDownloader}